Many different types and kinds of blood pressure cuffs have been known in the prior art. In use, prior known cuffs have been first positioned on a limb with the measuring area of the cuff--the area containing the inflatable bladder--placed against blood vessels of the limb. The cuff is then wrapped snugly around the limb and the ends of the cuff secured so as to hold the cuff in position on the limb during the measurement. The cuff is then inflated, and a reading of the blood pressure taken.
Blood pressure cuffs suffer from several significant problems, such as difficulty in providing a single cuff which can be fitted to a wide variety of sizes of limbs of greatly differing circumference, shifting of position of the cuff when it is tensioned and secured about a limb, and discomfort caused by the pressure of the cuff on a limb.
The problem of fitting limbs of widely differing size has been dealt with conventionally by providing an assortment of different size cuffs. However, in order to fit small children as well as substantially everyone else, including large adults, three or four different size cuffs are required. Thus, inventory problems are common. Also, sometimes the size of the limb is misjudged, and the conventional cuff must be removed and a different size cuff must be located and then applied to the limb. Such inconveniences are unwanted and are unduly time consuming.
The problem of shifting of the cuff occurs during the wrapping, tensioning and securing of a pressure cuff to a limb. Conventional cuffs oftentimes shift and become somewhat askew in their final wrapped position on the limb. Such improper positioning of the cuff on the limb may result in inaccurate blood pressure measurements. Additionally, when the cuff is askew in its final wrapped position, the cuff is not tightly secured in place. Especially in polygraphy, a loosely wrapped cuff adversely affects the sensitivity of the cuff to detect blood pressure, or relative changes in blood pressure when used with polygraph apparatus. The greater the wrap tension of the cuff, the better the coupling of the cuff bladder to the arterial vessels of the limb so that impulses of the cardiovascular system of the body are transmitted to the bladder with little loss of energy. Thus, an improperly wrapped cuff is much less sensitive for detecting blood pressure, or relative changes thereof in the body.
Pressure cuffs used with polygraph instruments are pressurized to a sufficiently high level to restrict severely the flow of blood in the limb, thereby producing a tourniquet effect. As a result, discomfort or pain, caused by compressed tissue, is directly proportional to the area of the compressed tissue and the applied pressure. Blotches or discolorations on the surface of the limb are oftentimes produced and are caused by ruptured blood vessels and by blood flowing back to the heart through body tissues rather than through the cuff-constricted veins. So grave are these problems that at least one state requires specific time limits, such as four minutes, on the length of time that a cuff may be pressurized during a polygraph test. If the pressure of the cuff is reduced to ameliorate these problems, the accuracy of interpretation of the subject's responses to questions may be adversely affected.
In an attempt to overcome the problem of pain and discomfort associated with the use of a pressure cuff in polygraphy, polygraph instruments have been employed, using low-pressure cuffs and electronic equipment for detecting blood pressure variations. However, such polygraph apparatus suffers from the problem that greater sensitivity may show up spurious minor variations in blood pressure and thus the readings may be difficult to interpret.
In an attempt to overcome some of the foregoing problems associated with conventional pressure cuffs, a prior known cuff was designed to reduce the shifting of position during affixing it to a limb, and to fit many different size limbs. In this regard, reference may be made to U.S. Pat. No. 3,977,393 issued to V. E. Kovacic. As mentioned in the foregoing patent, shifting of position during affixing to a limb is reduced by providing the cuff with an elongated slot or hole in the band intermediate its ends to enable one end to be threaded through the slot so that both ends may be grasped and tension applied in opposite directions to secure the cuff about the limb.
In order to fit different size limbs, the Kovacic cuff is accomplished by making the slot elongated, so that the cuff has a range of different circumferences, determined by the extreme ends of the slot.
However, the Kovacic cuff can be used only with limbs having circumference falling within a relatively narrow range of circumferences. Very large limbs cannot be accommodated due to the physical dimensions of the cuff. Limbs smaller in diameter than a limiting size imposed by the geometry of the slot of the cuff cannot be accommodated. In order to fit the cuff to a smaller limb, such as a child's or woman's limb, requires that the slot not be used. Instead, the cuff is wrapped in place about the limb, by overlapping the ends without the use of the double-tensioning feature. As a result, the cuff may shift, and inaccurate readings may result. Moreover, one may attempt to use the slot on a small limb, only to discover that the cuff cannot be tightened about the limb. Thus, the cuff must be removed entirely and be re-applied without the aid of the double-tensioning feature.
Therefore, it would be highly desired to have a pressure cuff, which fits many different size limbs in a single operation, which is easy to apply with little or no circumferential shifting, and which reduces greatly discomfort and discoloration associated with its use. Such a cuff should be relatively inexpensive to manufacture.